Supersonic compressors



Nov. 10, 1964 BOURQUARD 3,156,407 ISUPERSONIC couPREssoRs Filed July 6,1959 s Sheets-Sheet 1 III "'IIIIIIIIIIIIIII' I 1 111/ IIIIIIIIIIIIIIIIIIJ IIIII/ IIIIIIIIIIIIIIIIIII III, wally/111111111111 Nov. 10, 1964 F.BOURQUARD 3,

SUPERSONIG COIIPRESSORS Filed July 6, 1959 5 Sheets-Sheet 2 Nov. 10,1964 F. BOURQUARD 3,156,407

' suransonxc couPasssoas Filed. July 6, 1959 3 Sheets-Sheet 3 I V'IIIIIlI/llllllllllm 3,156,407 SUPERSONIC COMPRESSORS Fernand Eourquard,Courhevoie, France, assignor to Commissariat a lEnergie Atomique, Paris,France, a

French organization Filed July 6, 1959, Ser. No. 825,166 Claimspriority, application France July 7, 1958 4 Claims. (Cl. 230-120) Thepresent invention relates to supersonic compressors for gaseous fluids,that is to say to compressors including at least one blading (supersonicblading), either fixed or movable, through which the relative velocityof the fluid with respect to the blades is higher than the localvelocity of sound at least in some portions of the passages formedbetween said blades.

The invention is more especially but not exclusively concerned withcompressors of this type including a blading, either fixed or movable,arranged in such manner that the velocity of the fluid at the inletthereof is supersonic.

The chief object of the present invention is to provide a compressor ofthis type which is better adapted to meet the requirements of practicethan those used up to now, especially concerning the stability ofoperation.

According to this invention, each of the passages provided between theblades of the supersonic blading, including an intermediate zone inwhich a normal shock wave is produced (so that the flow in the passageis supersonic upstream of said zone and subsonic downstream thereof),has its portion located upstream of said intermediate zone shaped insuch manner as to produce in said last mentioned portion a succession ofexpansion waves, that is to say of waves creating an acceleration of thefluid on its way toward said shock wave.

Preferred embodiments of the present invention will be hereinafterdescribed with reference to the accompanying drawings, given merely byway of example and in which:

FIG. 1 is a part view showing the development of the annular members ofa supersonic axial flow compressor made according to the invention, thisview being a section by a cylinder coaxial to the compressor and cuttingthe blades at mid-height thereof.

FIG. 2 is a similar section of a portion of a rotor bladingcorresponding to a modification.

FIG. 3 shows the velocity triangle characterizing the operation of thiscompressor.

FIG. 4 is a section of a portion of a centrifugal compressor accordingto the invention by a plane perpendicular to the axis of saidcompressor.

The axial flow compressor diagrammatically illustrated by FIG. 1includes the following elements:

On the one hand, a set of fixed guide blades 1 which are preferablyslightly inclined in such manner that the fluid as it leaves said bladeshas an absolute velocity Va inclined in a given direction, for instanceat an angle of approximately 10, and

On the other hand, a rotor including a set of blades 2 located oppositethe set of guide blades 1, said blades 2 having a velocity U (atmid-height of said blades 2 in a direction opposed to that toward whichthe guide blades 1 are inclined, the value of this velocity U being suchthat the mean relative velocity Vr of the fluid entering the passagesbetween the rotor blades 2 is supersonic.

By way of example, illustrated by the velocity triangle of FIG. 3, if ais the local velocity of sound at the inlet of rotor 2, the velocity Vamay be given a value of approximately 0.7a and the velocity U is given avalue of about 1.2a.

Thus the velocity Vr of the fluid at the inlet of the passages betweenblades 2 has a value of about 1.6a, that is to say is supersonic.

} United States Patent 3,156,407 Patented Nov. 10, 1964 It is known thatit has already been endeavoured, by a suitable shaping of the blades 2of such a rotor, in particular by giving a divergent shape to the endportion of every passage P provided between two successive blades, tocreate during the operation, in each of the respective passages P, anormal shock wave D (recompression wave) downstream of which thevelocity of flow becomes subsonic whereas the velocity upstream of saidshock wave is supersonic.

In a supersonic blading of this kind, Where normal shock waves areformed, it is advantageous to produce, upstream of the normal shock waveD of every passage, an intermediate transient zone where take placephenomenons which modify the pressure and velocity of the gaseous streamflowing through said transient zone.

For this purpose, it has been suggested to shape the supersonic blades,in their portions located upstream of the normal shock wave, in suchmanner as to create, in every passage, upstream of said normal shockwave, one or several oblique shock waves (recompression waves) intendedto slow down the gaseous flow and to increase its pressure before itreaches said normal shock wave.

Such an arrangement, which has the advantage of increasing the pressureof the gaseous flow gradually from the first recompression oblique waveto the normal shock wave, involves a lack of stability of said normalshock wave for some conditions of operation, in particular in the caseof a sudden increase of the How in the downstream direction, this lackof stability preventing the normal shock wave from being maintained inthe vicinity of the supersonic throat.

The object of the present invention is to overcome this drawback at thecost of a small supplementary loss of pressure in the gaseous flow.

According to this feature, blades 2, in the portion of each of themlimiting the transient zone of every passage P and located upstream ofthe normal shock wave D are arranged in such manner as to produce insaid transient zone, instead of recompression waves, expansion waves d dd (only some of which are shown on FIG. 1). The effect of theseexpansion waves is to accelerate the flow of fluid upstream of thenormal shock wave D (whereas the recompression waves according to priordevices slowed down the flow in the transient zone) thus furtherpermitting, at the place of said normal shock wave, a distribution ofvelocities of regular divergence.

It results therefrom that the normal shock wave D has a convexity turnedtoward the downstream direction, such a convexity being favorable to thestabilization of said shock wave. When shock wave D is urged in thedownward direction by an increase of the flow rate of the gaseousstream, it moves slightly in this downstream direction, thus increasingthe suction produced immediately upstream of said normal shock wave bythe successive actions of expansion waves d d d etc.

Shock wave D having been moved toward higher velocities, a more violentshock is produced at the passage through said shock wave D, so thatthere is an increased pressure drop which compensates for the increaseof suction in the downward direction.

The normal shock wave D is thus stabilized in its new position.

It will be understood that such an operation is inherent in the presenceof expansion waves upstream of the normal shock wave because, when thetransient zone is occupied by recompression waves, the pressure drop atthe passage through the normal shock wave is the lower as the shock waveis moved a greater distance in the downward direction by suction.Therefore in this case, the normal shock wave is unstable in case ofsudden suction thereof in the downward direction.

Concerning now the means to be provided'for creating, in said transientzone, the expansion waves that are to accelerate the gaseous fluid flowthrough said zone, they may be obtained by giving at least the suctionface E of every blade, in the portion thereof located in the transientzone, a suitable convexity, the portion of the suction face locatedupstream of this convex portion being preferably rectilinear andextending substantially in the direction of the inlet velocity Vr of thegaseous fluid stream.

Thus the suction face E of every blade 2 includes a substantiallyrectilinear flat area starting from the blade leading edge, parallel tothe velocity Vr of the gaseous stream entering the passages between theblades, this flat area extending from the leading edge A of the blade tothe point B from which an expansion wave d starting from the suctionface of the blade that is considered reaches the next blade at theleading edge A thereof. After this flat area, the suction face E ofblade 2 includes a slightly convex portion BC (the respective tangentsat B and C making an angle of approximately 7 with each other). Thisconvex portion BC pr ferably has a constant curvature and its end C isadvantageously at the point where an oblique shock wave A C startingfrom the leading edge A of the next blade reaches the blade suction facethat is being considered. Finally the blade suction face E includes,after this convex portion BC, a rectilinear portion CD extending atleast as far as the place where the normal shock wave D is located. Thisrectilinear portion increases the deflection produced by convex portionBC (the angle between the tangent at C to BC and the rectilinear portionhaving advantageously the same order of magnitude as the dihedral angleof the leading edge of the blade). This rectilinear portion CD extendsbeyond point D possibly as far as the trailing edge F of the blade. Itmay also be followed by a curvilinear portion arranged in accordancewith the laws of subsonic aerodynamics so as to obtain the desiredresult at the ou let of the blading.

As for the pressure face I of the blade, it may be given a substantiallyrectilinear shape from the leading edge A to the trailing edge F.

According to the modification illustrated by FIG. 2, the convexity of 7above referred to with reference to FIG. 1 may be distributed betweenthe two opposite walls that limit the transient zone, these two wallsincluding for instance'convex portions BC and BC, each of whichcorrespond to a change of direction of 3.5". Each of said convexportions may be followed by rectilinear portions forming the divergentdiffuser passage.

Anyway, there is obtained in every passage P, upstream of the normalshock wave .0 thereof, an increasing velocity gradient for the airstream, accompanied by an expansion, then, after the shock wave, arecompression and fan-like distribution of the velocities, which aresuddenly reduced by the passage of the fluid through the shock wave,such an arrangement making it possible to stabilize the normal shockwave.

FIG. 4 shows a centrifugal compressor made according to the presentinvention. This compressor includes a bladed rotor 3 delivering agaseous fluid at supersonic relative velocity to a fixed diffuserblading.

Preferably, at the inlet of every passage P formed between twosuccessive blades, there is obtained for the flow of the fluid amovement of permanent velocity such that the surfaces of equalvelocities and equal pressures are of revolution about an axis of rotor3. For this purpose, the inlet portion AB of the suction face of everyblade is given the shape of a concave spiral arc producing recompressionwaves directed toward rotor 3, the end point B of this are correspondingto the last compression wave BA capable of reaching said rotor withoutbeing stopped by the leading edge A of the next blade.

After point B, the suction face E of the blade include a convex areaintended to create, in the transient zone located upstream of the normalshock wave D", expansion waves capable of accelerating the flow of thefluid, the end point C of this convex portion (the curvature of whichmay, as above, correspond to a deflection of 7) being preferably thepoint where the oblique shock wave starting from the leading edge A ofthe next blade reaches the pressure face E of the blade that is beingconsidered. After this convex area, there is provided a rectilinear flatarea which increases the deflection by an angle approximately equal tothe angle of the leading edge, this last mentioned flat area extendingas far as the trailing edge of the blade.

Thus point B constitutes an inflexion point whereas point C constitutesan angular point in the profile of the lade.

As for the pressure face I of every blade, it may include a rectilinearfiat area starting from the leading edge and continued by a convexportion limiting, together with the oppositely disposed suction face ofthe next blade, a subsonic diffuser in which may possibly be disposed aguide blade 5.

Whatever be the type of compressor made according to the invention, thepassages P between the blades may be either of rectangular transversesection or of ovoid or circular transverse section.

In a general manner, while I have, in the above description, disclosedwhat I deem to be practical and cflicient embodiments of my invention,it should be well understood that I do not wish to be limited thereto asthere m'ignt be changes made in the arrangement, disposition and form ofthe parts without departing from the principle of the present inventionas comprehended Within the scope of the accompanying claims.

What I claim is:

1. A supersonic axial flow compressor for a gaseous fluid whichcomprises, in combination, a casing, two coaxial annular members mountedin said casing adjacent to each other in the axial direction anddefining an annular flow duct for said gaseous fluid through said twomembers successively in said axial direction, the downstream memberbeing a rotor, blades carried by said rotor and extending across saidflow duct to form between them a plurality of passages for said gaseousfluid, and guide blades carried by the upstream member and arranged toguide said fluid, fed thereto at a predetermined velocity to give it asit leaves said guide blades a velocity represented by a given vector,each of said rotor blades comprising on the suction face thereof asubstantially flat area extending from its leading edge and parallel tothe vector which is the resultant of the above mentioned vector and of avector representing the relative velocity of said rotor blade leadingedge at working speed with respect to said upstream member, thevelocities represented by the two last mentioned vectors being such thatthe resultant velocity is supersonic, the fore portion of each of saidpassages being convergent and the rear portion divergent in thedirection of the gaseous fluid flow, with a throat region between saidportions, so as to produce a normal shock wave rearwardly of saidconvergent portion, downstream of which shock wave the fluid flow issubsonic, said suction face of each of said rotor blades comprising,after said flat area, a slightly convex area extending from said flatarea to said throat portion, said flat and convex areas being arrangedto produce, in said convergent portion of said passage, a succession ofexpansion waves creating an acceleration of the gaseous fluid flowingpast them to reach said throat region, said convex area beginning at thepoints from which an expansion wave starting from said suction facereaches the leading edge of the next blade facing said suction face.

2. A supersonic axial flow compressor for a gaseous fluid whichcomprises, in combination, a casing, two

coaxial annular members mounted in said casing adjacent to each other inthe axial direction and defining an annular flow duct for said gaseousfluid through said two members successively in said axial direction, thedownstream member being a rotor, blades carried by said rotor andextending across said flow duct to form between them a plurality ofpassages for said gaseous fluid, and guide blades carried by theupstream member and arranged to guide said fluid, fed thereto at apredetermined velocity to give it as it leaves said guide blades avelocity represented by a given vector, each of said rotor bladescomprising on the suction face thereof a substantially flat areaextending from its leading edge and parallel to the vector which is theresultant of the above mentioned vector and of a vector representing therelative velocity of said upstream member at Working speed with respectto said rotor blade leading edge, the velocities represented by the twolast mentioned vectors being such that the resultant velocity issupersonic, the fore portion of each of said passages being convergentand the rear portion divergent in the direction of the gaseous fluidflow, with a throat region between said portions, so as to produce anormal shock wave rearwardly of said convergent portion, downstream ofwhich shock wave the fluid iiow is subsonic, said suction face of eachof said rotor blades comprising, after said flat area, a slightly convexarea extending from said flat area to said throat portion, and, aftersaid convex area, a flat area extending at least as far as the placewhere said normal shock wave is produced, said flat and convex areasbeing arranged to produce, in said convergent portion of said passage, asuccession of expansion waves creating an acceleration of the gaseousfluid flowing past them to reach said throat region, said convex areabeginning at the points from which an expansion wave starting from saidsuction face reaches the leading edge of the next blade facing saidsuction face.

3. A supersonic axial flow compressor for a gaseous fluid whichcomprises, in combination, a casing, two coaxial annular members mountedin said casing adjacent to each other in the axial direction anddefining an annular flow duct for said gaseous fluid through said twomembers successively in said axial direction, the downstream memberbeing a rotor, blades carried by said rotor and extending across saidflow duct to form between them a plurality of passages for said gaseousfluid, and guide blades carried by the upstream member and arranged toguide said fluid, fed thereto at a predetermined velocity to give it asit leaves said guide blades a velocity represented by a given vector,each of said rotor blades comprising on the suction face thereof asubstantially flat area extending from its leading edge and parallel tothe vector which is the resultant of the above mentioned vector and of avector representing the relative velocity of said upstream member atworking speed with respect to said rotor blade leading edge, thevelocities represented by the two last mentioned vectors being such thatthe resultant velocity is supersonic, the fore portion of each of saidpassages being convergent and the rear porat least as far as the placewhere said normal shock wave is produced, said flat and convex areasbeing arranged to produce, in said convergent portion of said passage, asuccession of expansion waves creating an acceleration of the gaseousfluid flowing past them to reach said throat region, the pressure facesof said rotor blades being of flat rectilinear shape from the leadingedge to the trailing edge of each of said blades, said convex areabeginning at the points from which an expansion wave starting from saidsuction face reaches the leading edge of the next blade facing saidsuction face.

4. A supersonic axial flow compressor for a gaseous fluid whichcomprises, in combination, a casing, two coaxial annular members mountedin said casing adjacent to each other in the axial direction anddefining an annular flow duct for said gaseous fluid through said twomembers successively in said axial direction, the downstream memberbeing a rotor, blades carried by said rotor and extending across saidflow duct to form between them a plurality of passages for said gaseousfluid, and guide blades carried by the upstream member and arranged toguide said fluid, fed thereto at a predetermined velocity to give it asit leaves said guide blades a velocity represented by a given vector,each of said rotor blades comprising on the suction face thereof asubstantially flat area extending from its leading edge and parallel tothe vector which is the resultant of the above mentioned vector and of avector representing the relative velocity of said upstream member atworking speed with respect to said rotor blade leading edge, thevelocities represented by the two last mentioned vectors being such thatthe resultant velocity is supersonic, the fore portion of each of saidpassages being convergent and the rear portion divergent in thedirection of the gaseous fluid flow, with a throat region between saidportions, so as to produce a normal shock wave rearwardly of saidconvergent portion, downstream of which shock wave the fluid fiow issubsonic, said suction face of each of said rotor blades comprising,after said flat area, a slightly convex area extending from said flatarea to said throat portion, and, after said convex area, a fiat areaextending at least as far as the place where said normal shock wave isproduced, said flat and convex areas being arranged to produce, in saidconvergent portion of said passage, a succession of expansion tiondivergent in the direction of the gaseous fluid flow,

with a throat region between said portions, so as to produce a normalshock wave rearwardly of said convergent portion, downstream of whichshock wave the fluid flow is subsonic, said suction face of each of saidrotor-blades comprising, after said flat area, a slightly convex areaextending from said flat area to said throat portion, and, after saidconvex area, a flat area extending waves creating an acceleration of thegaseous fluid flowing past them to reach said throat region, thepressure faces of said rotor blades being of convex shape from theleading edge to a point upstream of} said throat region, said convexarea beginning at the points from which an expansion wave starting fromsaid suction face reaches the leading edge of the next blade facing saidsuction face.

References Cited in the tile of this patent UNITED STATES PATENTS2,435,236 Redding Feb. 3, 1948 2,659,528 Price Nov. 17, 1953 2,934,259Hausmann Apr. 26, 1960 2,935,246 Roy May 3, 1960 FOREIGN PATENTS 459,043Italy Aug. 23, 1950 687,338 Great Britain Feb. 11, 1953 687,365 GreatBritain Feb. 11, 1953 776,676 France Jan. 31, 1935 1,106,834 France July27, 1955

1. A SUPERSONIC AXIAL FLOW COMPRESSOR FOR A GASEOUS FLUID WHICHCOMPRISES, IN COMBINATION, A CASING, TWO COAXIAL ANNULAR MEMBERS MOUNTEDIN SAID CASING ADJACENT TO EACH OTHER IN THE AXIAL DIRECTION ANDDEFINING AN ANNULAR FLOW DUCT FOR SAID GASEOUS FLUID THROUGH SAID TWOMEMBERS SUCCESSIVELY IN SAID AXIAL DIRECTION, THE DOWNSTREAM MEMBERBEING A ROTOR, BLADES CARRIED BY SAID ROTOR AND EXTENDING ACROSS SAIDFLOW DUCT TO FORM BETWEEN THEM A PLURALITY OF PASSAGES FOR SAID GASEOUSFLUID, AND GUIDE BLADES CARRIED BY THE UPSTREAM MEMBER AND ARRANGED TOGUIDE SAID FLUID, FED THERETO AT A PREDETERMINED VELOCITY TO GIVE IT ASIT LEAVES SAID GUIDE BLADES A VELOCITY REPRESENTED BY A GIVEN VECTOR,EACH OF SAID ROTOR BLADES COMPRISING ON THE SUCTION FACE THEREOF ASUBSTANTIALLY FLAT AREA EXTENDING FROM ITS LEADING EDGE AND PARALLEL TOTHE VECTOR WHICH IS THE RESULTANT OF THE ABOVE MENTIONED VECTOR AND OF AVECTOR REPRESENTING THE RELATIVE VELOCITY OF SAID ROTOR BLADE LEADINGEDGE AT WORKING SPEED WITH RESPECT TO SAID UPSTREAM MEMBER, THEVELOCITIES REPRESENTED BY THE TWO LAST MENTIONED VECTORS BEING SUCH THATTHE RESULTANT VELOCITY IS SUPERSONIC, THE FORE PORTION OF EACH OF SAIDPASSAGES BEING CONVERGENT AND THE REAR PORTION DIVERGENT IN THEDIRECTION OF THE GASEOUS FLUID FLOW, WITH A THROAT REGION BETWEEN SAIDPORTIONS, SO AS TO PRODUCE A NORMAL SHOCK WAVE REARWARDLY OF SAIDCONVERGENT PORTION, DOWNSTREAM OF WHICH SHOCK WAVE THE FLUID FLOW ISSUBSONIC, SAID SUCTION FACE OF EACH OF SAID ROTOR BLADES COMPRISING,AFTER SAID FLAT AREA, A SLIGHTLY CONVEX AREA EXTENDING FROM SAID FLATAREA TO SAID THROAT PORTION, SAID FLAT AND CONVEX AREAS BEING ARRANGEDTO PRODUCE, IN SAID CONVERGENT PORTION OF SAID PASSAGE, A SUCCESSION OFEXPANSION WAVES CREATING AN ACCELERATION OF THE GASEOUS FLUID FLOWINGPAST THEM TO REACH SAID THROAT REGION, SAID CONVEX AREA BEGINNING AT THEPOINTS FROM WHICH AN EXPANSION WAVE STARTING FROM SAID SUCTION FACEREACHES THE LEADING EDGE OF THE NEXT BLADE FACING SAID SUCTION FACE.